Sugar refining



Patented Dec. 25, 1945 SUGAR ammo Ralph W. Shai'or, New York, N. Y.,assignor to The Dorr Company, a corporation of Delaware No Drawing.Application November 21, 1941, SerlalNo. 419,910

4 Claims. (on. 127-46) the raw sugar suspended impurities havingashyielding characteristics and especially colorimparting substances. Soan object of this invention is to effect an increased yield of refinedsugar per unit of raw sugar treated, and another object is to effect animproved quality of refined sugar that is substantially ash free.

In sugar refining, it is usually customary to make use of bleachingagents, followed by suspcnded-solids-separating steps, since the use ofsuch agents ordinarily forms precipitates. Therefore, other objects ofthis invention are to reduce the quantity of bleaching and other relatedre-agents used and to eliminate certain costly operations necessitatedby the use of bleaching agents.

A new process or" treating sugar-making juices has lately come intopractice which comprises the removal of non-sugars or non-sucroseconstituents by the use of organolites. An organolite is anionic-exchanger granular material of organic nature. These are made useof by subjecting the juice sequentially to a bed of such organoliteoperating in the hydrogen cycle and another bed of such materialoperating in the hydroxyl cycle. The H-ion bed is a cation exchanger,while the OH-ion.bed is an anion exchanger. When exhausted or saturatedwith cations collected from the juice, the cation bed is regeneratedwith a strong mineral acid that discharges the collected cations fromthe bed and restores H-ions to the bed. The anion bed is regeneratedwith a strong base such as sodium hydroxide that discharges thecollected anions from the bed and restores OH-ions to the bed. Besidesremoving ionic material from the juice, these beds also removecolor-imparting constituents from the juice. Such organolite treatmentis disclosed in patent application of F. N. Rawlings, Serial No.376,717, filed January 31, 1941.

Another object of this invention, therefore, is to treat raw sugarproduced by said organolite process with modified bleaching processesthat meet the foregoing objects.

For an understanding of the environment of this invention, it may bestated that commercial raw sugar in being refined is usually treated bya method wherein the raw sugar is dissolved to produce a syrup,suspended solids are separated from the solution phase of such a syrupby filtration, the clarified syrup is then subjected to the action of anoxidizing bleaching or decolorizing agent, such as calcium hypochlorite,the resulting mixture is treated with an acid and a salt capable ofadjusting the pH to a point optimum for bleaching efflciency andprecipitating a large portion of the ash-forming constituents introducedas components of the bleaching reagents employed, the so-formedprecipitate is separated from the bleached solution phase to produce asubstantially clear syrup with a minimum of color, the oxidizingpotentialities of any residual bleaching agent are neutralized, andfinally refined sugar is crystallized from the treated syrup. Therun-ofi syrup from the crystallization step is often used for washing,or amnating, the raw sugar to be refined, thus producing a washed rawsugar of higher purity.

By way of further explanation, it is obvious that when, as aboveoutlined, the bleaching agent, calcium hypochlorite, is added to thesyrup and the chlorine component thereof has affected the desiredbleaching action, all components of said bleaching agent remain in thesyrup as non-sugar impurities. This is undesirable because it reducesthe amount of sugar which can be recovered in refined form from thatsyrup. Therefore, in past practice, it has been customary to employ areagent, such as calcium acid phosphate, which will react with a portionof the bleaching agent components to form a precipitate, filter saidprecipitate from the syrup thereby eliminating a large portion of thisundesired eifect.

The method herein set forth provides a means whereby the precipitationstep of past practice may be eliminated.

So a further object of this invention is to modify the refining processto reduce the filtering operations to a minimum as well as to reduce theamount, of bleaching and other reagents used. A still further object isto make use of bleaching agents not heretofore usable. Also to make useof bleaching agents that produce no precipitate.

This invention may be said to revolve about a combination of certainchemical bleaching and certain ionic exchanger steps. One order of thesegives on type of result, while another order gives a difierent result.One order can be used on one starting material, while another order canbest be used on a different startin material. And, finally, dependingupon the character desired of the end product, a different order may beused. By order is meant not only the sequence of bleaching and ionicexchanger treatment, but sequence of respective steps in each. Raw sugarreferred to herein means raw sugar available in the sugar market today.

. A type of treatment is herein contemplated by this invention whereinthe bleaching reagent is of a character that precipitation may beorganolite treatment thus reducing the quantity part for theash-precipitating reagents. The

syrup may have its pH adjusted with non-precipltating reagents such asHCl and NaOH to an optimum point for emcient bleaching with somenon-precipitating hypochlorite bleaching reagent such as sodiumhypochlorite or chlorine gas. Neutralization of residual hypochlorite orchlorinated products may be done with a, reducing reagent such as sodiumhydrosuli'ite to leave the syrup free from strong oxidizing agents priorto subiecting the bleached syrup to sugar crystallizing operations. usedon the syrup prior to its being bleached with bleaching reagents, orsubsequent thereto or both. However, the raw sugar must be in the formof syrup before it is amenable to organolite treatment. Since thisis so,the process of this invention is usable on a syrup of melted raw sugaror a syrup of afllnated raw sugar (which means raw sugar mixed withrun-off syrup from the crystallizer for thus raising the purity of thewashed sugar).

The organolite treatment of syrup to be made use of in the practice ofthis invention has to do with beds that make use of granular ionexchange material that is of organic nature and is of that type nownewly called organolites in distinction from the inorganic baseexchangers heretofore known as zeolites. In extracting nonsugars andespecially dissolved salts from sugar solutions or syrup. two main typesof ion-exchange beds are used. One that is called the cation exchangerbed is characterized by its use of ionic exchanger material thatoperates on the hydrogen-ion cycle and is adapted to collect from thejuice positively charged ions (called cations) represented generally bycalcium, magnesium, sodium and potassium. That is, as syrup is suppliedto the cation exchanger bed (or cell that contains the bed) so as topass through it and out therefrom, cations'of dissolved salts of thejuice exchange themselves for hydrogen ions of the exchanger until theexchanger bed becomes depleted of its exchange capacity and is sosaturated with cations that it ceases substantially to exercise furtherexchange activity. Thereupon the cation bed must be regenerated bycontact with a regenerant in the form of an ionized strong acid such ashydrochloric or sulphuric acids. During regeneration, the reverseequilibrium process takes place in the exchanger, namely, the cationtaken up by the exchanger with hydrogen ions of the acid regenerant sothat the cations flow from the bed until the bed is completely rechargedwith hydrogen ions.

Syrup that passes from the cation bed has had its impurity content ofcations substantially removed and replaced by a molar equivalent ofhydrogen ions, but it yet contains sulphates, chlorides and other suchnegative ionic impurities. So the juice substantially rid of itspositive ionic or cation impurities that have been left behind. iscontacted with an anion exchanger bed or cell that operates in thehydroxyl cycle. In passing The organolite treatment may be the bed untilthe anion bed becomes saturated with sulphates, chlorides and the likeanions. Thereupon the saturated anion bed must be regenerated by contactwith some ionized hydroxide or carbonate, especially sodium hydroxide orcarbonate. During regeneration the reverse equilibrium process takesplace, namely, the residual chloride and sulphate anions in the bedexchange with hydroxyl ions of the basic regenerant so that thecollected negative ions or anions flow from the bed until the anion bedis recharged with hydroxyl ions. In passing through the anion bed. thesyrup is substantially rid of its negative or acid-forming anions sincethey have been left in the exchanger. Thus, the basic or positive ionsof the syrup are removed from it while passing through a cationexchanger bed and the negative or acid-forming ions are removed from itwhile passing through a subsequent anion exchanger bed. In other words,the cations of the salts are replaced by H-ions (in the hydrogen-ioncycle) while the anions of the salts are replaced by OH-ions (in thehydroxyl-ion cycle), with the net result that the salts are replacedwith HOH (or H2O), that is the molar equivalent in pure and evaporablewater. Other substanceaare also removed from the juice by thisparticular treatment. that surprisingly are non-ionic, such ascolorimparting constituents and colloids.

These exchanger operating cycles (namely the hydrogen-ion cycle of thecation exchanger and 5 the hydroxyl-ion cycle of the anion exchanger)can be described in chemical nomenclature, and for the sake ofsimplicity and illustration, the removal of potassium chloride amongother salts from the syrup will be taken as an example. The

a organic resinous cation exchanger o organolite is assumed to havetaken up H-ion in the course of its previous regeneration. Uponcontacting the syrup with the exchanger, the latter will exchange itsH-ion for the potassium cation of the salt and form hydrochloric acid(HCl) according to the following equilibrium: Let :2: represent theorganic structure or framework of the cation exchanger. Then:

(A) E+K++CP XK- l-H++Cl- The syrup according to Equation A is beingacidified because of its reaction with the cation This represents thatthe exchanger is again ready for contacting with syrup, while thepotassium compound is in the spent regeneration liquor. Other acids,such as H2804, I-INO: may be used instead of HCl for regeneration of thecation exchanger with corresponding results.

By contact of the syrup with the organic resinous anion exchanger ororganolite containing replaceable hydroxyl groups, the anion of the acid(HCl) present in the syrup according to Equation i assume A istaken upby the exchanger in exchange for the OH-group, and the followingequilibrium established: Let Y represent the organic structure orframework' of the anion exchanger. Then:

According to Equation C the juice is being deacidified as it is beingfreed from the acid that had previously formed in the cation exchangeraccording toEquation A. In this way the cation. as well as the anion ofthe salt constituting the impurity, are removed from the syrup and re-'It will be understood that instead of HCl, another suitable strong acid,for instance, H1804. may be used as a regenerant for the cationexchanger. In that instance sulfuric acid will reform as syrup is beingtreated by the cation exchanger. I

In the course of a complete operating cycle each of these exchangers, ifexhausted, is to have the residual syrup therein displaced from theexchanger bed with wash water, and if deposits have collected on theexchanger granules they are to be washed out, before the exchanger isub- ,iected to contact with the regenerant solution. Again, ifregeneration is completed, the residual regenerant is to be displacedand washed out from the exchanger with water, before the exchangeris'again contacted with the syrup. In this way undesirable reactions inthe exchanger bed can be avoided and the exchanger be kept in regularcyclic operation with substantially undiminished efllciency.

The exhaustion or saturation of a fresh exchanger bed with the solutionflowing downtreat the more the cation'cxchang'erhed at temperature notin excess of 35' C. and it and 15 C. as a practical minimumtemperature."

Forpracticing this invention, various orders and combinations oftreatment steps will be described in the following examples, eachcomplete and independent of the other:

r. The objective of the following combination resides in the avoidanceof a precipitate being yielded in the syrup during the bleachingoperation to the end that the bleached syrup may be treated fora secondtime by the exchanger process to eliminate the-ionizable materialsintro-- duced into the syrup-by the addition of the bleaching agentsboth primary and secondary' This process is set forth in the followingexample:

The method of refining raw' sugar of substantially'96" or higher puritywhich comprises all!- nating raw sugar with a syrup having a puritylower than that of the sugar and having been 1 produced during aprevious operation of this wardly therethrough proceeds in continuousfashion from the top to the bottom of the exchanger body. Hence thereexists, approximately speaking, a dividing line or relatively narrowzone of transition between the upper exhausted or saturated portion ofthe exchanger body and the lower non-exhausted 0r non-saturated portionof that body. This dividing line or zone keeps shifting downwardlythrough the exchanger body as the continuously-through-fiowing solutionleaves an increasing exhausted exchanger portion behind as it advancesthrough a correspondingly decreasing portion of non-exhausted orstill-ac tive exchanger. However, as the dividing line is notnecessarily a sharp one, there will be noticed a slowing-down of theexchange intensity as the break through point of the exchanger is beingThe su ar solution or process, for the purpose of increasing the-purityof the sugar; melting the ai'finated sugar to produce anafllnated-sugarsyrum separating suspended solids from the solution phaseof the afilnated-sugar syrup if there be present an amount suflicient tointerfere with the subsequent operations; then subjecting the substan-.tially clear afllnated-sugar syrup at temperatures such as to avoidsubstantial inversion of sucrose to the action of anionic-exchanger'material operating in the hydrogen cycle to removecations and to the action of an ionic exchanger material operating inthe hydroxyl cycle to remove anions from the syrup for the purposes ofpurifying and partially decolorizing the syrup to produce asubstantially ion-free syr p; then treating the ion-free syrup with areagent such as HCl suitable for adjusting the pH of the syrup to theoptimum point of efficient bleaching with- ,out the formation of aprecipitate and also with I the mixture, all to produce a bleachedsyrup;

then neutralizing under influence of mechanical agitation, the oxidizingpotentialities of any hypochlorite and chlorinated products which maythen remain in the bleached syrup with a suitable reagent so as toproduce a syrup free from strong oxidizing agents; subjecting thebleached syrup to the action of said two types of ionic exchangers for asecond time to remove the ions introduced during these final bleachingsteps to produce a highly purified, ion-free, colorless syrup;subjecting the colorless syrup to crystallization by concentrationprocedure to produce successive crops of-crystals of refined sugar untilsuch operations produce a syrup of such color and low purity unsuited tofurther production of such crystals; and returning said low-purity syrupto the afiination step of 'a subsequent operation to the process. 1

This method should result in a high yield of the highest quality ofrefined sugar that is totally ash-free and of the best color obtainablefrom a given raw sugar. The quantity of required bleaching agents isreduced to a minimum. By using bleaching agents which produce no pre-'cipitate, costly and tedious filtering operations are reduced to aminimum.

II. The following method has for its objective the elimination of thetedious filtration steps necessitated by using the precipitatablereagents employed in preceding method (see Example V).

The method of refining raw sugar of 96' or 1 higher purity which hadbeen produced from melting the sugar to produce a substantially ion-1free syrup, treating under the influence of mechanical agitation andpreferably at temperatures between 25 and 50 C. such ion-free syrup witha reagent suitable for adjusting the pH of the syrup to the optimumpoint for efilcient bleaching without the formation of a precipitate,and with an aqueous solution of a non-precipitating hypochloritesuitable'for removing the coloring matter therein both without theintroduction into the mixture of a precipitate; neutralizing theoxidizing characteristics of the excess hypochlorite and chlorinatedproducts with a suitable reducing reagent so as to minimize their actionduring subsequent operations; separating suspended solids from thesolution phase of said decolorized syrup if an amount be presentsufilcient to interfere with subsequent operations; subjecting thesubstantially clear decolorized syrup at temperatures such as to avoidsubstantial inversion of sucrose to the action of an ionic-exchangermaterial operating in the hydrogen cycle to remove cations and t0 theaction of an ionic exchanger material operating in the I hydroxyl cycleto remove anions from said syrup for the purposes of purifying same toproduce a substantially colorless, ion-free syrup; and subiecting saidcolorless ion-free syrup tocrystallization by concentration procedure toproduce successive crops of crystals of reflned sugar until suchoperations produce a syrup of such color and low purity unsuited tofurther production of such crystals.

With a normal consumption of bleaching reagents, a maximum yield ofhighest grade ashfree refined sugar will be obtained.

The bleaching or decolorizing agent should be used in a quantitydepending upon the quantity of color constituents present and the degreeof decolorization desired, of from one-eighth to one pound of activechlorine per thousand pounds of sugar melted. The syrup should betreated with the bleaching agent while preferably at room temperaturesor between 25 and 50 C. and also under the influence of mechanicalagitation. Agitation should also be used when the reducing agent isadded to the syrup. The reducing or neutralizing agent that also shouldbe non-precipitating, is preferably sodium hydrosulfite. Where the acidand salt is mentioned, monocalcium phosphate is preferred. And when anon-precipitating pI-I-adjusting agent is mentioned, hydrochloric acidor sodium hydroxide is preferred, as the case may be. When used, thetemperature of the juice should be between substantia1ly'25 and 50 C. Iffiltration or defecationis made use of to remove precipitates from thesyrup, it should be done with the temperature of the syrup not in excessof 70 C. And finally, the cation stage of the organolite treatmentshould preferably be carried out as heretofore explained, with the syrupat a temperature of substantially or less (down to say 15 C.) todiscourage any substantially great inversion of sucrose of the syrup toglucose and the like inverts.

Exchangers of the type contemplated for use in connection with thepresent invention, are

substantially stable in the presence of acids and alkalis. g

The organic cation or base exchangers and organic acid or anionexchangers which may be used in this process include a variety of both.

Among the cation exchangers which may be used are:

1. Cation exchangers produced by the treatment of humic compounds withsulfur com-.

pounds which introduce acid sulfur groups into the humic substance sotreated, such as treating lignite with concentrated sulfuric acid orequivalent. Materials of this class which have been stabilized byspecial treatment to prevent color throwing arealso applicable.

2. Cation exchangers produced by treating materials containing aromaticphenols. such as tannins, with sulfuric acid, petroleum acid sludgefuming sulfuric acid or equivalent agent which causes both thecondensation of phenolic material and the introduction of acid sulfurgroups to the condensed material.

3. Cation exchangers produced by the condensation of aromatic phenolswith an aldehyde with or without the aid of catalysts.

4. Cation exchangers produced by the condensation of aromatic phenolswith an aldehyde and with or without the aid of catalysts and into whichacid sulfur groups have been introduced prior to, simultaneous with orsubsequent to condensation.

5. The cation exchanger produced by the Resinous Products Co. ofPhiladelphia, under the name or identification of Amberlite IR. 1.

6. Cation exchanger of organic resinous nature as exemplified in the U.S patent to Holmes, No. 2,191,853, where the exchanger is described as asynthetic resin of the polyhydric phenol formaldehyde type which issulphited to a degree such that its sulphur content is not less than2.4%.

A variety of organic anion exchangers which may be used comprises:

1. Anion exchangers produced by the condensation of an aromatic aminewith an aldehyde.

2. Anion exchangers produced by the condensation of a mixture of anaromatic amine and a mono or disaccharlde with an aldehyde.

3. Anion exchangers in which the active constituent is a basic dyestuif,such as the aniline blacks, which are insoluble in water and in aqueousacids and alkalls.

4. The anion exchanger produced by the Resinous Products Co. ofPhiladelphia, under the name or identification of Amberllte IRA.

5. Anion exchanger of organic resinous nature as exemplified in the U.S.'patent to Adams and Holmes, No. 2,151,883, describing the exchangerasan insoluble resinlike product .obtained by the reaction offormaldehyde with an aromatic amine.

I claim:

1. The process of refining raw sugar which comprises treating syrup ofraw sugar with a hypochlorite bleaching agent of the non-precipitablekind whereby ash-forming ions are introduced in thesyrup, and subjectingthe syrup to the action of a cation exchanger material operating in thehydrogen cycle and then to the action of an anion exchanger materialoperating in the hydroxyl cycle whereby said ash-forming ions areremoved from the syrup.

2. The process according to claim 1, with the addition that inconjunction with the. bleaching treatment the syrup is treated with a pHadjust- 7; ing agent sufficient to establish optimum bleachingconditions, and then treated with a reducing substance to react with andthus offset the oxidizing effect of any excess of the bleaching agent;said exchange treatment being effective to remove from the syrup ionicmatter introduced by said pH adjusting agent and said neutralizingagent.

3. The process according to claim 1, with the addition that the syrupafter the bleaching treatment is treated with a substance to react with10

